This is a P41 renewal proposal to continue the National Biomedical Center for Advance ESR Technology (ACERT). Four principal areas of Technology Research and Development (TR&D) will be emphasized. They consist of 1) Structure of Proteins and Protein Complexes by Pulse Dipolar ESR; 2) Protein and Membrane Dynamics and Protein Folding Dynamics by Time-Resolved and Two-Dimensional ESR; 3) Very High-Frequency, High-Field ESR for Multi-frequency Studies of Dynamics in Proteins and Membranes and 4) ESR Microscopy for Biological and Biomedical Applications. Extensive Driven Biomedical Projects and other collaborations with biomedical researchers will greatly benefit from these TR&D's, which in turn are driven by the DBP needs for the new and improved ESR technologies. Thus, there is an important synergism amongst the TR&D's and the DBP's. The technologies being developed at ACERT are in many respects unique in the world. The extensive DBP's and collaborative/service projects at ACERT will continue to bring these modern ESR methods to the forefront of biomedical research, especially as the additional challenges are addressed in the TR&D's. This includes our plans to increase throughput of our facilities for which there are growing demands. The plans for dissemination and training address the need to bring these new technologies to other laboratories in the USA and elsewhere in addition to making the facilities available to outside scientists, publishing and advertising the results of the Center and running workshops on the new methodologies.